1. Field of the Invention
The present invention relates, in general, to a microwave oven with halogen lamps and, more particularly, to a microwave oven designed to uniformly heat food in a cavity and to reduce the negative effect of the heat, emanating from the halogen lamps, on the interior equipment of the microwave oven.
2. Description of the Prior Art
As well known to those skilled in the art, a variety of cooking devices have been proposed and used. Of the cooking devices, the primary one is cooking ware, which is designed to have a shape suitable for containing food therein and is laid on a heater so as to be directly heated by the heater while cooking.
In addition, several types of electric cooking devices, designed to directly or indirectly utilize electric power while cooking, have been proposed and used. An example of conventional electric cooking devices is a microwave oven using a magnetron as a heat source. In such a microwave oven, the magnetron is electrically operated to generate microwaves and applies the microwaves to food in a cavity, thus allowing the microwaves to cause an active molecular motion in the food. Such an active molecular motion in the food generates molecular kinetic energy, thus heating and cooking the food. Such microwave ovens are advantageous in that they have a simple construction and are convenient to a user while cooking, and easily and simply heat food in the cavity. The microwave ovens are thus somewhat preferably used for some cooking applications, such as a thawing operation for frozen food or a heating operation for milk requiring to be heated to a desired temperature.
However, such microwave ovens also have the following problems. That is, the ovens have a defect in their heating style in addition to limited output power of the magnetron, and so it is almost impossible to freely or preferably use them for a variety of cooking applications, without limitation. In a detailed description, the conventional microwave ovens only utilize a magnetron as a heat source, thus undesirably having a single heating style. In addition, the output power of the magnetron, installed in such ovens, is limited to a predetermined level. Therefore, the conventional microwave ovens fail to provide a quick and highly effective cooking operation. During a cooking operation utilizing such a microwave oven, food in a cavity is heated at its internal and external portions at the same time, and this may be an advantage of the oven in some cases. However, such a heating style may result in a disadvantage while cooking some food. For example, the cooking style of the conventional microwave ovens is not suitable for cooking pizza for reasons that will be described in more detail later herein. Another disadvantage, experienced in the conventional microwave ovens, resides in that the ovens exceedingly remove moisture from food.
In an effort to overcome the above-mentioned problems, several types of microwave ovens, having another heat source in addition to a magnetron, have been proposed and used. For example, a microwave oven, having a convection heater in addition to a magnetron in a casing and originally designed to be used for a variety of cooking applications, has been proposed. However, such a convection heater only acts as a single heat source, thus failing to allow the microwave oven to have a variety of operational functions.
In a brief description, the conventional microwave ovens are problematic in that they have a single heating style utilizing microwaves, limited output power of a magnetron, and cause the evaporation of an exceeding amount of moisture from food. The microwave ovens, having another heater in addition to a magnetron, fail to completely overcome the problems experienced in the conventional microwave ovens.
In order to solve the problems of the conventional microwave ovens, another type of microwave oven, utilizing a light wave, has been proposed. In this microwave oven, a lamp, wherein at least 90% of the radiation energy has a wavelength of not longer than 1 .mu.m, is used as the additional heat source. In said microwave oven, both visible rays and infrared rays from the lamp are appropriately used, and it is possible to preferably heat the exterior and interior of food while making the most of characteristics of the food. An example of such a lamp is a halogen lamp.
Due to a difference in wavelengths between the infrared rays and visible rays emanating from a halogen lamp, the heating styles for the exterior and interior of food are different from each other. While cooking pizza utilizing a halogen lamp, it is possible to appropriately heat the pizza in a way such that the exterior of the pizza is heated to become crisp and the interior is heated to be soft while maintaining appropriate moisture.
FIG. 1 is a conventional microwave oven utilizing a halogen lamp as an additional heat source. As shown in the drawing, the microwave oven comprises two halogen lamps 12 installed on the top wall 10 of a cavity 2. The microwave oven uses the light waves, radiated from the lamps 12, for heating food in the same manner as that described above, with the characteristics of the light waves remaining the same as that described above.
A light reflection plate 16 is installed at a position above the halogen lamps 12, thus reflecting any light waves, emanating upwardly from the lamps 12, back downwardly into the cavity 2. A plurality of light transmitting holes 18 are formed on the top wall 10 of the cavity 2, with the halogen lamps 12 being held on the top wall.
In the conventional microwave oven of FIG. 1, two lower halogen lamps (not shown), having the same construction as that of the two upper lamps 12, are provided on the bottom wall 11 of the cavity 2.
That is, upper and lower halogen lamps are respectively provided on the top and bottom walls 10 and 11 of a cavity 2 at corresponding positions in a conventional microwave oven. However, the microwave oven, having such a typical lamp structure, is problematic as follows.
In the typical halogen lamp structure, two halogen lamps are positioned on each of the top and bottom walls 10 and 11 of the cavity 2 at the center. The two lower halogen lamps, positioned on the bottom wall 11 of the cavity 2, may overheat a turntable motor (not shown) within the cavity 2. That is, the cavity 2 is provided with both a turntable used for supporting food thereon and a turntable motor used for rotating the turntable. The two lower halogen lamps, provided on the center of the bottom wall 11, are positioned around the turntable motor. Therefore, heat, emanating from the lower halogen lamps, is directly transmitted to the turntable motor, thus undesirably overheating the motor. Since a conventional halogen lamp generates heat having a high temperature of not lower than 1000.degree. C., the turntable motor may be thermally and seriously damaged during a cooking operation of the microwave oven.
In addition, the upper and lower halogen lamps are provided on the top and bottom walls of the cavity at corresponding positions, and so the lamps may fail to uniformly heat food within the cavity. That is, the food is laid on and rotated by the turntable, while the position of the upper and lower lamps is fixed. The lamps thus concentrate heat to a portion of the food, and so the food fails to be uniformly heated or cooked.